This invention pertains to a metathesis process for producing unsaturated alcohols (olefin alcohols).
Unsaturated alcohols, such as homo-allylic and allylic alcohols, are useful intermediates in the preparation of synthetic rubbers, surfactants, fragrances, and thermoplastic polyurethanes.
In recent years the chemical industry has directed attention towards replacing petroleum-based chemical feedstocks with non-petroleum-based chemical feedstocks. Along these lines investigations have focused on converting natural and genetically-modified seed oils into useful industrial organic chemicals. It is known, for example, that unsaturated fatty acid esters derived from seed oils can undergo cross-metathesis reactions with lower olefins, such as C2-8 olefins, in the presence of a metathesis catalyst to form reduced-chain olefins and reduced-chain unsaturated esters. International patent application publication WO-A-96/04289, for example, discloses such metathesis reactions wherein the catalyst contains monodentate ligands, that is, ligands having one binding site to a central catalytic metal. As an illustrative example, methyl oleate is disclosed to undergoes cross-metathesis with ethylene (ethenolysis) in the presence of dichloro-3,3-diphenylvinyl-carbene-bis(tricyclohexylphosphine)ruthenium (II), to form 1-decene, a reduced chain α-olefin, and methyl 9-decenoate, a reduced chain unsaturated ester. Homo-metathesis reactions are also disclosed, wherein one molecule of unsaturated fatty acid ester is metathesized with a molecule of identical unsaturated fatty acid ester. As an example, methyl oleate is disclosed to undergo homo-metathesis to form 9-octadecene and dimethyl-1,18-octadec-9-enedioate.
The metathesis of hydroxy-substituted unsaturated fatty acids and fatty acid esters derived from seed oils also produces unsaturated alcohols (olefin alcohols) that are different from the reactant hydroxy-substituted unsaturated fatty acids and fatty acid esters. Such unsaturated alcohol products may be value-added depending upon market conditions and end-uses. Cross-metathesis typically produces an unsaturated mono-alcohol; whereas homo-metathesis typically produces an unsaturated polyol. As an example, the cross-metathesis of methyl 12-hydroxy-octadec-9-eneoate (methyl ricinoleate) with ethylene produces a homo-allylic alcohol, namely, 1-decene-4-ol, and an unsaturated ester, namely, methyl 9-decenoate. Disadvantageously, however, when a hydroxy-substituted unsaturated fatty acid or fatty acid ester is metathesized, a catalyst turnover number is achieved that tends to be low for practical applications. For the purposes of this invention, the term “catalyst turnover number” shall refer to the number of moles of metathesis product formed per mole of metathesis catalyst employed.
In view of the above, it would be desirable to discover an improved process of homo-metathesizing or cross-metathesizing a hydroxy-substituted unsaturated fatty acid or fatty acid ester for the purpose of preparing an unsaturated alcohol product that is different from the hydroxy-substituted unsaturated fatty acid or fatty acid ester reactant. It would be more desirable if the unsaturated alcohol product was an allylic mono-alcohol or allylic polyol, or a homo-allylic mono-alcohol or homo-allylic polyol. It would be even more desirable if such a process exhibited an improved catalyst turnover number, as compared with present day processes. An improved catalyst turnover number should enhance the potential for commercializing the metathesis of hydroxy-substituted unsaturated fatty acids and fatty acid esters, thereby providing a route to useful industrial organic chemicals via non-petroleum-based chemical feedstocks, such as, natural or genetically-modified seed oils.